Molecular epidemiology of ovine papillomavirus infections among sheep in
Southern Italy
Abstract
Ovine papillomaviruses (OaPVs) were detected and quantified, for the
first time, using droplet digital polymerase chain reaction (ddPCR) and
real-time quantitative PCR (qPCR) via liquid biopsy of 165 clinically
healthy sheep. OaPV DNA was detected in 126 blood samples
(~76.4%). DdPCR detected OaPV DNA in 124 samples; in
only two additional samples positive for real-time qPCR, ddPCR failed to
detect the presence of any OaPVs. In 70 of the positive samples
(~55.6%), a single OaPV infection was observed, 12 of
which were caused by OaPV1 (~17.1%) and 14 by OaPV2
(20%). OaPV3 was responsible for 19 single infections
(~27.1%), and OaPV4 for 25 single infections
(~35.7%). Multiple OaPV coinfections were observed in
56 (~44.4%) positive samples. OaPV coinfections caused
by two genotypes were observed in 31 positive samples
(~55.4%), with dual OaPV3/OaPV4 infection being the
most prevalent as seen in 11 blood samples. In addition, five
OaPV1/OaPV4, four OaPV1/OaPV2, four OaPV2/OaPV3, four OaPV1/OaPV3, and
three OaPV2/OaPV4 dual coinfections were also detected. OaPV
coinfections by triple and quadruple genotypes were detected in 24
(~42.8%) and only one (~1.8%) of
coinfected blood samples, respectively. Multiple infections caused by
OaPV1/OaPV3/OaPV4 genotypes were the most prevalent, as observed in 12
(50%) blood samples harboring triple OaPV infections. This study showed
that ddPCR is the most sensitive and accurate assay for OaPV detection
and quantification thus outperforming real-time qPCR in terms of
sensitivity and specificity. Therefore, ddPCR may represent the
molecular diagnostic tool of choice, ultimately providing useful
insights into OaPV molecular epidemiology and field surveillance.